Eric Woster (WOSTER@worldnet.att.net) used the following steps to extend the range of the RCDLR: Based on a frequency of about 315 Megahertz, a quarter wave antenna length will be about 240mm or 9.5inches. You need to make a close coupled loop that matches the internal antenna loop dimensions with two quarter wave tails on the ends of the loop. In this way the extra antenna is outside of the RCDLR box. The RCDLR (Remote Control Door Lock Receiver) module is located in the rear package shelf (rear deck). You'll need to undo the two plastic clips (squeeze and push back through the holes). You may have to remove the rear package shelf carpet and padding that is above the RCDLR.

Find a thin piece of stiff cardboard and cut a rectangle the size of the front surface of the RCDLR.
Glue (don't staple) a single 360' loop of braided 20AWG wire to the board with long ends. The ends should hang off of the cardboard by at least a foot.
Snip the ends of both wires to make them extend from the edge of the cardboard by 9 to 9.5 inches.
After the glue has dried, pull the back of the back seat out, lift the back package shelf carpet up just a little, and secure the carboard loop to the front of the RCDLR with tape or double-sided tape, and let the wire ends hang off at the top. The wire ends can be streched out and taped down or just held in place by the package shelf.
Reassemble.
This should nearly triple the range to the rear of the vehicle.
A longer antenna won't help without some fancy ground plane effects and ugly designs. Running the antenna somewhere else will increase the antenna length unless a coaxial cable is used.